1. Field of the Invention
This invention relates generally to devices for supporting elongated structures and more specifically to devices for insulating and supporting pipes.
2. Description of the Prior Art
Modern construction, particularly in industrial plants and power generation facilities, frequently requires the use of insulated pipes for carrying hot or cold liquids or gases. This insulation is necessary to prevent the transfer of heat between the pipe and the liquid or gas contained therein in the surrounding environment. Additionally, modern construction codes frequently require that all pipes carrying materials of temperatures differing significantly from the ambient temperature must be insulated.
In a typical construction application an insulated pipe will be displaced from the support surface such that it may be necessary to support it by virtue of hangers if the pipe is to be supported from above, by cantilevers if the pipe is to be supported from the side, and by pedestals if the pipe is to be supported from below. In each of these cases it is necessary that a firm contact restricting the pipe from movement in the directions perpendicular to its axis to be achieved between the support member and the pipe. While direct metal-to-metal welding or clamping is strongest and securest and thus preferable for this purpose alone, several difficulties arise in connection with this practice in applications wherein the pipe must be insulated. Even if the clamp or weld is subsequently wrapped or coated with insulation, there remains a conductive heat transfer path through the clamp or weld to the support structure, thus generating a significant heat transfer between the environment and the pipe. This substantially defeats the purpose of the insulation.
Various attempts have been made in the prior art to achieve firm lateral and longitudinal support of a pipe while maintaining the proper insulation thereof. Examples of these attempts are to be found in U.S. Pat. No. 3,530,899 issued to Dillard Breeding, U.S. Pat. No. 3,559,694 issued to Fred J. Volberg, U.S. Pat. No. 3,848,897 issued to William McClellan, U.S. Pat. No. 3,372,894 issued to Chris J. Botsolas and U.S. Pat. No. 3,058,860 issued to Donald P. Rutter. Each of the devices described in the above-mentioned patents attempts to provide a purchase or support means for a pipe while maintaining the pipe in relative isolation from the environment by the use of an interior insulating material.
It is to be noted that in a completely insulated application the weight of the pipe will be borne directly by the insulating material. In order to maintain an effective barrier to thermal conductance from the pipe to the support structure it is necessary that the insulation be the only material actually contacting the pipe. Consequently, it is necessary that the insulating material utilized have significant load bearing capacity so as to prevent crushing of the insulating material and diminution of its insulating characteristics. Consequently, the insulating material utilized in such supports must be of significantly greater density and load carrying ability than material which may be utilized in intermediate points wherein no load carrying capacity is required. Such higher density load carrying material is more costly to manufacture and machine than the lower density insulation utilized on the remainder of the pipe.
Another difficulty which the prior art pipe supports have attempted to address is the ease and security of installation of the support member on the pipe while maintaining complete insulation surrounding the pipe. The prior art cited utilizes various methods of achieving this goal as well. These include hinged support devices which close on the pipe, flexible framing on the support device such that it may be wrapped over an independent insert of insulation material, a flexible spring type outer coating of the support materials so as to hold the insulation in place against the pipe and devices wherein two portions are placed together and held by clamps. Each of these methods have disadvantages. These disadvantages include the necessity of a flexible and/or resilient outer coating material which limits the strength of the support and the requirement of additional hardware such as hinges and/or clamps which must be manufactured and assembled separately, thus increasing the cost and complexity of the devices.
A further difficulty in pipe insulating and support devices is the achievement of an effective vapor barrier. This vapor barrier is the effective air seal which prevents the exterior air, and consequently the water vapor contained therein, from coming into contact with the pipe surface. In the case of a cold pipe, water laden air contacting the pipe will result in condensation on the pipe surface which will then seep into the insulating material and diminish its insulating capacity. In the case of a hot pipe, air contacting the pipe will be heated up in such a manner that when it then contacts the cooler inner surface of the support material holding the insulation in place, condensation may take place on this surface with the same effect. Therefore, it is highly desirable to prevent the significant influx of air against the pipe surface.
None of the prior art devices utilized for supporting and insulating pipes solve all of these problems. None can satisfy the extremely high support requirements, particularly in nuclear facilities where earthquake standards must be maintained, while maintaining easy on-site assembly, easy and economical manufacture and an effective vapor barrier.